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Origins & Protists
USC FSH BISC121 Midterm 2 - Origins of Life & Protists
| Question / Vocabulary | Answer / Definition |
|---|---|
| Background extinctions | Naturally occurring slow extinctions, one species at a time, about ~96% of extinctions |
| Mass extinctions | The extinction of a large number of species rapidly, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt. |
| Big-5 mass extinctions | 1. 444 mya 2. ~355 mya 3. 251 mya 4. 200 mya 5. 65.5 mya |
| Permian mass extinction | ca. 250 mya, occurred in 5 million to a few thousand years. 96% of marine life died |
| Cretaceous mass extinction | 65 mya, extinction of dinosaurs, caused by an iridium-layer asteroid impact that hit the coast of Mexico |
| When was the first evidence of cellular life? | 3.5 billion years ago |
| What were the first cells? | Prokaryotic autotrophs |
| Photoautotrophs | Organisms that produce energy from sunlight |
| Chemoautotrophs | Organisms that produce energy using simple compounds, eg. ammonia |
| Heterotrophs | Organisms that obtain energy from existing organic molecules, eg. sugars |
| When did the atmosphere start being saturated with oxygen? | 2.5 billion years ago |
| What was the earliest source of atmospheric oxygen? | Cyanobacteria |
| How was the earliest atmospheric oxygen produced? | Photosynthesis with oxygen reacting with dissolved iron and precipitating out to form banded iron formations |
| When were the oldest eukaryotic cells? | approx. 2 billion years ago |
| What group were the oldest eukaryotic cells most closely related to? | Archaeans |
| How did the nuclear membrane in eukaryotes form? | Infolding of the plasma membrane in prokaryotes |
| Endosymbiosis | Mitochondria and plastids such as chloroplasts were formerly small prokaryotes that were engulfed by host cell |
| Evidence for endosymbiosis | Mitochondria and plastids have their own DNA to replicate in a similar way to bacteria |
| When did the first multicellular eukaryotes appear? | 1.5 billion years ago |
| What were the oldest known fossils of multicellular eukaryotes? | Tiny multicellular algae from around 1.5 b.y.a. |
| When did more diverse multicellular organisms start emerging? | around 600 million years ago (Precambrian age) |
| Protists | A paraphyletic group of organisms in the domain Eukarya but are not plants, animals or fungi, including algae, dinoflagellates, diatoms, parasites |
| Are protists unicellular or multicellular? | Most are unicellular, but some are multicellular |
| Algae | A polyphyletic group of photosynthetic protists, eg. red algae |
| Phytoplankton | Planktonic algae that rely on water currents in oceans and rivers for movement |
| Secondary symbiosis | Eukaryotic heterotrophic cells engulfing autotrophic eukaryotic cells, forming new organisms, eg. dinoflagellates (engulfed red algae) |
| Dinoflagellates | A monophyletic group of unicellular protists that have cellulose cell walls and flagella in their groove |
| Red tides | Toxic algal dinoflagellate blooms |
| Diatoms | A monophyletic group of unicellular photosynthetic phytoplankton with glass-like cell walls of silica, extremely abundant and important for CO2 absorption in the ocean |
| Brown algae | A monophyletic group of multicellular algae closely related to diatoms and are often large, attached to the bottom of oceans in the form of kelp forests |
| Red algae | A monophyletic group of algae who have pigments giving them a red color, found much deeper in the sea than other algae |
| Green algae | A monophyletic group of algae with bright green chloroplasts that are closely related to land plants, eg. chlorophytes (sea lettuce) |
| What is Euglena an example of? | Mixotrophy, protists that can switch between heterotrophy and autotrophy, it can switch its photosynthetic processes on or off |
| Parasites | A group of protists that live on or in a host organism and gets its food from or at the expense of its host |
| Examples of parasites | Trypanosoma, plasmodium |
| Trypanosoma | Example of a parasitic protist genus, causes sleeping sickness in humans by infecting the bloodstream and nervous system through the tsetse fly vector, which disrupts our sleep cycle (related to Euglena) |
| Plasmodium | Example of a parasitic protist genus that causes malaria in humans by infecting and lysing RBC through mosquitoes as a vector, causing symptoms of fever, sweating and chills |
| Plasmodium life cycle | Most stages are haploid, with formation of gametes, fertilization and meiosis happening within the mosquito |
| What happens during mosquito bites? | Immature Plasmodium infects the liver first, then matures |
| Where is the second infective stage of mosquito bites? | In the red blood cells |
| Unikonta | A taxonomic supergroup that contains many protist groups (amoebozoans), but also animals and fungi |
| Amoebazoa | A monophyletic phylum that includes slime molds and various amoebae |
| Amoebae | A polyphyletic group of unicellular heterotrophic protists that engulf food particles via phagocytosis and move by using projected pseudopodia |
| Mycetozoa | A polyphyletic group of slime molds that were once thought to be fungi, are terrestrial but need a lot of moisture, have fruiting bodies with sporangia (fungus-like), contain two main branches |
| Plasmodial slime molds | A monophyletic group of slime molds with a main plasmodial stage that grows on decomposing material, engulfing bacteria and other organic material by phagocytosis |
| Life cycle of plasmodial slime molds | Main stage has large cytoplasm undivided by membranes, contains many diploid (2n) nuclei, produces fruiting bodies with haploid (n) spores |
| Cellular slime molds | A monophyletic group of slime molds that are microscopic, and have barely visible fruiting bodies common in soils around the world, often used as an experimental model for studying the evolution of multicellularity |
| Main stage of cellular slime molds | Feeding stage has solitary cells (haploid) mainly feeding on bacteria. Once food is depleted, the cells form a multicellular aggregate 'slug' that functions as a unit, whose cells are still separated by membranes, produces fruiting bodies with sporangia |
Created by:
elephantmonkey66
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